Science has a history of evolving as new data and tools for data analysis become available. Yet science and scientist today, as in the past, share fundamentally differing opinions on a diversity of topics. Among them, whether a comet is a mere “dirty snowball” or an elegant coma of electrically conductive plasma which during its long period on the outer reaches of the solar system acquires a strong negative charge and then, as it approaches the inner limit of its orbit accelerating through the electric field of the sun begins to discharge the plasma surrounding it, producing its familiar bright tail.
Even the evidence for periodic mass extinctions is strongly contingent on arbitrary decisions concerning the culling of data, the stratigraphical boundaries, and the definition of what extinction is. The science of climate change on this planet is as subject to our true lack of understanding regarding evolutionary epochs and the bio-chemical evolutionary processes that govern our magnificent world in our little solar neighborhood. Indeed, an interested party with a click of their mouse can read a veritable smorgasbord of opinions often presented as “fact” regarding the state of planetary health on the beautiful blue marble we inhabit.
It is clear the last two and a half million years have been marked by many global climate oscillations, between warmer and cooler conditions. The trend of oscillations appears to be merely the continuation of a pattern of variability extending well back into the Tertiary period and possible beyond. (e.g., Kennet, 1995). During the last few million years, the length and amplitude of these climate cycles has increased (e.g., Crowley and North, 1991; Hodell and Venz, 1992). Large global interglacial-glacial-interglacial climate oscillations have been recurring at approximately a 100,000 year precocity for the last 900,000 years (e.g., Berger et al, 1993; Mudelse and Schulz, 1997), though each individual cycle has had its own idiosyncrasies in terms of the magnitude of changes (e.g., Lyle et al, 1992).
During the last 150,000 years, at least a few large climate changes certainly occurred on the timescale of individual human lifetimes, the most well established and best studied of this being the Younger Dryas and various Holocene climate shifts. Despite how our understanding has grown, particularly in the past decade, greater knowledge of how frequently such sudden events have occurred, and under what general circumstances, is required before a greater understanding can be reached.
Unfortunately time doesn’t appear to be on our side in this endeavor. Never before have we been spectators witnessing the most rapid melting of glacial ice in contemporary history. Handicapped by our lack of knowing how often decade-timescale changes occurred in the recent geological past we remain handicapped in our ability to forecast and plan for future events. It is not justifiable to speak of what “will” definitely happen in the future even though the public and policy makers are looking for certainties. Even if we knew everything there was to know about past climate mechanisms, it is likely we would not be able to forecast such events confidently into the future. The very nature of the ocean-climate system is chaotic; runaway changes coming from miniscule differences in the initial conditions creating probabilities rather than definite models of what may happen.
Never before has a human factor played such a large part on what these miniscule differences and runaway changes may be. No data sets are available of previous events that encompassed the proliferation of a carbon producing Industrial Age. The fear is that relatively small anthropogenic changes in high-latitude temperature as a result of Greenhouse gases might switch North Atlantic circulation and alter the Gulfstream during such natural fluctuations. It is clear that past “kill rates” for species during previous climatic events has been as high as 77% and 96% for the larger extinctions that the biosphere is forced through narrow bottlenecks and that recovery from these events is accompanied with fundamental changes in biotic composition.
If we consider the “best of cases” of our biological past history, our lack of understanding of how this evolutionary process works, combined with several centuries of manmade impact on our fragile, responsive ecosystem we might consider that we are well beyond the catastrophic tipping point. Given this perspective, we might perhaps examine just what “planning for a sustainable future” looks like in the midst of an event horizon that is already occurring. For truly, it is only now with the very most current data sets, in the midst of the event, that we are beginning to be able with a modicum of certainty to predict what is likely to happen in the next decade. Beyond that, the probability of where we might be as a planet and a species is very much a probabilistic roll of the dice.